1209721 has 4 divisors (see below), whose sum is σ = 1216000. Its totient is φ = 1203444.

The previous prime is 1209709. The next prime is 1209739. The reversal of 1209721 is 1279021.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1209721 - 2⁹ = 1209209 is a prime.

It is a super-3 number, since 3×1209721³ = 5311007492523337083, which contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1209692 and 1209701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1209781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2841 + ... + 3238.

It is an arithmetic number, because the mean of its divisors is an integer number (304000).

2^1209721 is an apocalyptic number.

It is an amenable number.

1209721 is a deficient number, since it is larger than the sum of its proper divisors (6279).

1209721 is an equidigital number, since it uses as much as digits as its factorization.

1209721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6278.

The product of its (nonzero) digits is 252, while the sum is 22.

The square root of 1209721 is about 1099.8731745070. The cubic root of 1209721 is about 106.5520328811.

The spelling of 1209721 in words is "one million, two hundred nine thousand, seven hundred twenty-one".